Deformation characteristics and performance evolution of superalloy capillary drawn by electrically assisted microforming
Deformation characteristics and performance evolution of superalloy capillary drawn by electrically assisted microforming
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DOI：
10.1016/j.ijmecsci.2022.107912
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发表时间：
2022-11
影响因子：
7.3
通讯作者：
Yizhe Liu;B. Meng;M. Wan
中科院分区：
文献类型：
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作者：
Yizhe Liu;B. Meng;M. Wan
薄壁高温合金毛细管被认为是高超声速飞行器热交换器的核心部件。为了实现毛细管的精确高效制造，本研究提出了一种电辅助（EA）微成形工艺，并研究了电流下毛细管的变形特征和性能演变。实验结果表明，600℃的EA拉拔增强了晶粒协调变形能力和位错恢复，而800℃以上15s的EA退火实现了超快完全再结晶和梯度晶粒微观结构。微观结构的演变提高了延展性并避免了宏观缺陷，这与电塑性机制下位错活化能和晶界运动的降低有关。此外，电流对壁厚增加的抑制归因于摩擦系数的增加和氧化层的脱落，而电流通过形成超细晶粒、氧化峰和愈合槽来改善表面质量。与传统制造的毛细管相比，EA制造的直径0.9mm×58μm毛细管的表面质量、拉伸强度和延伸率分别提高了129.0%、31.1%和9.4%。由 EA 制造的毛细管集成的热交换器模块可以在 1 毫秒内将 25 m/s 的气流从 1000°C 冷却到 672°C。
Thin-walled superalloy capillaries are considered the core components of the heat exchanger in the hypersonic vehicle. To achieve the precise and efficient fabrication of capillaries, this study proposes an electrically assisted (EA) microforming process and investigates the deformation characteristics and performance evolution of capillaries under electric current. Experimental results show the EA drawing at 600 °C enhances the grain coordinated deformation capacity and dislocation recovery, while the ultrafast complete recrystallization and gradient grain microstructure are achieved by the EA annealing above 800 °C for 15 s. The microstructural evolution improves ductility and avoids macro defects, which is related to the reduction of activation energy of dislocation and grain boundary motion under the electroplastic mechanisms. In addition, the inhibition of the electric current on the increase in wall thickness is attributed to the increase in friction coefficient and the shedding of the oxide layer, while the electric current improves surface quality by forming ultrafine grains, oxidizing peaks, and healing troughs. Compared with the conventional manufactured capillaries, the surface quality, tensile strength, and elongation of the EA manufactured capillaries with the size of φ0.9 mm × 58 μm are increased by 129.0%, 31.1%, and 9.4%, respectively. A heat exchanger module integrated by the EA manufactured capillaries can cool the 25 m/s airflow from 1000 to 672 °C within 1 ms.